1. Field of the Invention
The present invention relates to a refrigerator that can store drinks in a supercooled state, and, more particularly, to a refrigerator, which can control a supercooling degree corresponding to user's taste or kinds of food, and a cooling control method thereof.
2. Description of the Related Art
Generally, a refrigerator or refrigeration apparatus serves to preserve various foods in a fresh state for a long period of time using chilled air, which is generated and supplied to storage spaces as a refrigerant absorbs heat from the surroundings via a phase change from liquid to vapor in a typical refrigeration cycle within the refrigerator. Recently, the refrigerator requires various additional functions as well as simple freezing, refrigerating, and preserving functions due to changes in lifestyle and taste of users. For example, the refrigerator has not only a function to preserve meats, fish, vegetables, kimchi, etc. in different states, but also a function to provide drinks (such as water, coffee, sikhae, juice, alcohol, etc.) in a supercooled state, which can be used for making, for example, a slush drink.
Drinks generally change in phase from liquid to solid below a freezing point under a pressure of 1 atm, but in some cases, it is into a supercooled state rather than the solid phase. Such a state where a liquid is in a supercooled state rather than in the solid phase below the freezing point is thermodynamically called a meta-stable state. When the drink is in the meta-stable state, the drink is in neither an equilibrium state nor a completely unstable state. Thus, if there is external disturbance, the drink instantaneously changes in phase from the supercooled state to the solid phase. In other words, when the supercooled drink is supplied to a cold cup, or subjected to impact or vibration, it changes to a phase not in a completely frozen or melted state, and such a drink is referred to as “slush.”
As such, a slush drink is generally made by supercooling a drink such as coffee, juice (strawberry, tomato, orange, apple, etc.), alcohol, etc. In this regard, Japanese Patent Laid-open Publication No. 2003-214753 discloses a refrigerator which can make such a drink in a supercooled state.
The refrigerator disclosed in the publication enhances an interior configuration of a body, and includes a chilled air supplying duct and chilled air suctioning duct respectively positioned on opposite sides of a storage compartment acting to preserve drinks therein, and a connection duct positioned on an upper side of the storage compartment to connect the chilled air supplying duct to the chilled air suctioning duct such that the chilled air supplying duct, the chilled air suctioning duct, and the connection duct constitute a path along which chilled air continuously circulates so as to maintain uniform temperature distribution within the storage compartment.
Meanwhile, although it is important for the refrigerator to preserve the drink in the supercooled state by maintaining the uniform temperature distribution within the storage compartment, it is more important for the refrigerator to supply a good quality slush drink to users by maintaining the supercooled state of the drink therein. For this purpose, it is necessary to maintain a temperature distribution according to time as uniform as possible within the storage compartment where the drink is preserved. In other words, even though the storage compartment has a uniform temperature when averaged over a period of time, if the temperature of the storage compartment varies over a wide range according to time, the supercooled drink may be frozen when the storage compartment is at the lowest temperature in this range, failing to produce the slush drink.
In addition, assuming that a temperature required for making the drink a supercooled state is −5° C., since a conventional supercooling refrigerator works using a constant operation pattern irrespective of user's taste in order to maintain the temperature of the storage compartment at −5° C., the user cannot select a supercooling degree of the drink even if he or she wants to adjust a ratio of supercooled grains (hereinafter referred to as a “slush level”) of the drink according to taste. As a result, with the conventional refrigerator, it is impossible to produce slush drinks (such as soft slush, general slush, hard slush, and the like) based on the user's taste, therefore failing to satisfy demands of the user.
Furthermore, the conventional refrigerator does not allow selective adjustment of the supercooling degree for maintaining an optimal supercooling temperature according to kinds of drink. Thus, it is impossible for the refrigerator to maintain an optimally supercooled state of the drink according to the kinds of drink (for example, coffee, juice, alcohol, and the like) or to the properties of containers (for example, a can or a glass bottle) which contain the drink.